AN INSIGHT INTO BEECH WOOD (Fagus sylvatica L.) DEGRADATION IN OUTDOORS, ABOVE GROUND, LONGTIME EXPOSURE Part 1: Degradation and influence of surface treatments revealed by nondestructive evaluation after 7 years

Beech (Fagus sylvatica L.) is an important woodspecies in Romania and research looking at thepossibilities of improving beech wood properties,especially durability and dimensional stability for anextension and diversification of utilisation towardsoutdoors, above ground applications (UC3) is of greatinterest. In this respect, it is important to study andunderstand the complex degradation phenomenaoccurring in time under these conditions and to testthe efficiency of the protective treatments inappropriate field tests. The research presented in thispaper aimed to evaluate the degradation of controland treated beech wood samples after seven yearsexposure in a modified L-Joint test. A non-destructiveevaluation system was employed and the differentaspects of the complex degradation of wood andcoatings, at macroscopic and microscopic level arepresented. The influence of a preservation treatmentwith a reference biocide product and further coatingwith an alkyd white paint and a brown alkyd semitransparentlasure is also discussed. Discoloration bymould and staining fungi and cracks were the maindegradation phenomena occurring on the externalfaces and in the joint area (tenon). Decay was presenton some treated samples, but not in a large extent,being ranked up to maximum average values of 2 in the tenon area and 1.5 on the external surfaces ofsome samples.The simple surface treatments applied had only aslight effect of reducing wood degradation over such along period of time. The best results were obtained forthe samples treated with biocide before finishing withthe alkyd white paint.In all cases the variability of wood as a naturalmaterial corroborated with the reduced number ofreplicate test samples (3) and possible smalldifferences in the actual testing conditions (moisturecontent variations between samples) should beconsidered when analysing the experimental results.